Fluid-actuated chuck-operating mechanism with a fluid lock

ABSTRACT

Fluid-actuated chuck-operating mechanism having an operationally turning cylinder with a piston therein, a swivel coupling with companion parts of which one part turns with the cylinder and the other part is operationally non-turning, with operating fluid under a given high-level pressure being supplied to the nonturning coupling part for its transmission through the latter part and its turning companion part to either cylinder end, and a unit having operating parts embodied in the non-turning coupling part and operative to lock the operating fluid in at least the chuck-closing cylinder end in case the pressure of the supply fluid to the latter should during a chuck operation drop from any cause below the pressure of the operating fluid in this chuckclosing cylinder end, and featuring a device for decreasing the pressure of the fluid in the chuck-closing cylinder end from the given high-level pressure to a given low-level pressure, which includes a manual control and a fluid passage by-passing the operating parts of the fluid-lock unit and leading directly to a fluid passage in the non-turning coupling part which, through a passage in the turning coupling part, is in permanent communication with the chuck-closing cylinder end, with this device being, on manipulation of the control, operative to vent the chuck-closing cylinder end until the pressure of the fluid therein reaches a given minimum level below the given low-level pressure, then discontinue venting of this cylinder end and apply to the latter fluid under the given low-level pressure.

ilnited States Patent 1191 Smithson [54] FLUID-ACTUATED CHUCK- OPERATING MECHANISM WITH A FLUID LOCK [75] Inventor: Gordon W. Smithson, Westerly, RI.

[73] Assignee: Cushman Industries, Incorporated,

Hartford, Conn.

[22] Filed: Nov. 22, 1971 [2|] Appl. No.: 200,992

Related U.S. Application Data [62] Division of Ser No. 30,636, April 22, I970, aban- UNITED STATES PATENTS 3,091,256 5/1963 Becker .j. ..91/32 x 3,156,255 11/1964 Gasquetetal..... 3,411,415 11/1968 Benjamin et al .91/420 Primary Examinerlrwin C. Cohen Attorney-Walter Spruegel 1451 May 29, 1973 [57] ABSTRACT Fluid-actuated chuck-operating mechanism having an operationally turning cylinder with a piston therein, a swivel coupling with companion parts of which one part turns with the cylinder and the other part is operationally non-turning, with operating fluid under a given high-level pressure being supplied to the nontuming coupling part for its transmission through the latter part and its turning companion part to either cylinder end, and a unit having operating parts embodied in the non-turning coupling part and operative to lock the operating fluid in at least the chuck-closing cylinder end in case the pressure of the supply fluid to the latter should during a chuck operation drop from any cause below the pressure of the operating fluid in this chuck-closing cylinder end, and featuring a device for decreasing the pressure of the fluid in the chuckclosing cylinder end from the given high-level pressure to a given low-level pressure, which includes a manual control and a fluid passage by-passing the operating parts of the fluid-lock unit and leading directly to a fluid passage in the non-turning coupling part which, through a passage in the turning coupling part, is in permanent communication with the chuck-closing cylinder end, with this device being, on manipulation of the control, operative to vent the chuck-closing cylinder end until the pressure of the fluid therein reaches a given minimum level below the given lowlevel pressure, then discontinue venting of this cylinder end and apply to the latter fluid under the given low-level pressure.

3 Claims, 7 Drawing Figures- PATENIEUHAYZSIQB SHEET 1 OF 2 1 FLUID-ACTUATED CHUCK-OPERATING MECHANISM WITH A FLUID LOCK This is a division of my copending application Ser. No. 30,636, filed Apr. 22, 1970, now abandoned.

This invention relates to fluid-operated chucks in general, and to fluid-operating mechanism of high-low operation for rotary chucks in particular.

Conventional fluid-operating mechanism for rotary chucks provide a cylinder, usually double-acting, and a piston therein, as well as a swivel coupling. The cylinder is customarily adapted for mounting on the chuckcarrying spindle of a lathe or the like so as to be turnable therewith, and the piston is adapted for operative connection with the jaw actuator of the chuck, while the swivel coupling has companion parts of which one part turns with the cylinder and the other part is connectible with two conduits and held against rotation, with these coupling parts being suitably ported for fluid flow between the conduits and the opposite sides, respectively, of the cylinder. There is also provided a control valve which for operation of the mechanism is connected with the two conduits and with a fluid pressure source, with the control valve being shiftable into two positions, in one position of which fluid from the source is admitted into the chuck-closing cylinder side and the opposite, chuck-opening, cylinder side is simultaneously vented, and in the other position fluid from the source is admitted into the chuck-opening cylinder side and the chuck-closing cylinder side is simultaneously vented.

There is also known fluid-operating mechanism of a type which will act to lock the operating fluid at least in the chuck-closing cylinder side whenever the pressure of the supplying fluid drops below a safe workgripping pressure from any cause whatever, including a leak or break anywhere in the supply line to this cylinder side. This is achieved by interposing a check valve in that part of the fluid passage which leads to the chuck-closing side of the cylinder, with the check valve opening to admit fluid into, but closing to block fluid flow from, this cylinder side, and providing a plunger which is subjected to fluid in the part of the fluid passage that leads to the chuck-opening side of the cylinder, and which on admission of operating fluid into this passage part for work release, opens the check valve for venting the chuck-closing cylinder side. The check valve and plunger are provided in a self-contained fluid-lock" unit which may either be directly embodied in, or formed separately and removably mounted on, the operationally non-turning part of the swivel coupling so as to be operationally stationary in either case, with this unit having conduit connections and being ported to link with the ports in the swivel coupling that lead to the opposite cylinder sides.

It is an object of the present invention to provide fluid-operating mechanism of the aforementioned type which lends itself to high-low operation, i.e., operation under manual control to supply the chuck-closing cylinder side with operating fluid under a given high-level pressure for an initial part of a machining operation on work held in an associated closed chuck, then under automatic or manual control vent the chuck-closing cylinder side until the pressure of the operating fluid therein drops to a given minimum level below a given low level, and then immediately supplying the chuckclosing cylinder side with operating fluid under pressure of the given low level for the conclusion of the machining operation on the work in the associated chuck.

Further objects and advantages will appear to those skilled in the art from the following, considered in conjunction with the accompanying drawings.

In the accompanying drawings, in which certain modes of carrying out the present invention are shown for illustrative purposes:

FIG. 1 is a section through fluid-operating mechanism embodying the present invention;

FIG. 2 is a section through a fluid-lock unit of the mechanism taken substantially on the line 2-2 of FIG.

FIG. 3 is a fragmentary section through the same unit taken on the line 3-3 of FIG. 2;

FIGS. 4 and 5 are fragmentary diagrammatic views, partly in section, of the mechanism of FIG. 1, but embodying different safe-operation devices;

FIG. 6 is a diagrammatic view, partly in section, of fluid-operating mechanism of high-low operation which embodies the invention; and

FIG. 7 is a fragmentary section through modified fluid-operating mechanism.

Referring to the drawings, and more particularly to FIGS. 1 to 3 thereof, the reference numeral 10 designates fluid-operating mechanism having a cylinder 12 with a piston 14 therein, and a swivel coupling 16 having companion parts 18 and 20, and including in this instance an antifriction bearing 22 with inner and outer races 24 and 26. The cylinder 12 is adapted for mounting on a chuck-carrying power spindle of a lathe or the like and, hence, is operationally turning, and the piston 14 has a rod 28 adapted for usual connection with a draw bar to operate a jaw actuator of the chuck (neither shown). The piston 14 is made to turn with the cylinder 12 by suitable provisions (not shown). The coupling part 18, on which the inner race 24 of the antifriction bearing 22 is mounted, is carried by, and in this instance formed integrally with, the cylinder 12 and, hence, turns with the latter, while the other coupling part 20, in which the outer bearing race 26 is mounted, is operationally non-turning. The non-turning coupling part 20 is formed in two sections 30 and 32 which at 34 are bolted together and straddle the outer bearing race 26 so as to be held against axial removal from the tuming coupling part 18. The coupling parts 18 and 20 have orifices to-be-described which lead to the interior of the cylinder.

The fluid-operating mechanism also provides a fluidlock unit 40 which is separate from the non-turning coupling part 20, but is mounted thereon so as to be operationally non-turning. The unit 40 is formed, preferably and advantageously, in two casing sections 42 and 44 and a cover section 46, of which the sections 42 and 46 are end sections having mounting surfaces 48 and 50, respectively, while section 44 is an intermediate section having opposite mounting surfaces 52 and 54 which in the assembled relation of the sections are adjacent the mounting surfaces 48 and 50 of the respective end sections 42 and 46, with suitable gaskets (not shown) being preferably interposed between adjacent mounting surfaces. The unit sections 42 to 46 are assembled by being removably secured to each other, as by bolts 56 (FIG. 2), with their mounting surfaces adjacent each other and preferably having interposed gaskets.

The end section 42 has an adapter end or surface 58 for mounting on a matching adapter end or surface 60 of the non-turning coupling part 20. The end section 42, and therewith the entire unit 40, is removably mounted on the non-turning coupling part 20, as by bolts 59, for example. Provided in the adapter surface 58 of the end section 42 are a bore 62 and a ringshaped recess 64 which is concentric with the bore 62. The end section 42 is further provided with two spaced, parallel fluid passages or bores 66 and 68 which in this instance extend with their axes normal to the axis of the bore 62 and lead into transverse passages or bores 70 and 72, respectively, which lead to the bore 62 and ring-shaped recess 64, respectively, and have their open ends 74 and 76 threaded for reception in this instance of plugs 78 and 80 (see also FIG. 3). The fluid passages 66 and 68 are at the mounting surface 48 counterbored to provide seats 82 and 84 for exemplary two check-valve assemblies 86 and 88, respectively. Since both check-valve assemblies are identical, only one will be described in detail. Thus, the valve assembly 86 provides a cylindrical body 90 which is fittedly received in the seat 82 and has a fluid passage 92 with an interposed valve seat 94, with the valve proper being preferably a ball 96 which is normally urged against the seat 94 by a spring 98. Accordingly, the valve 96 will permit fluid flow to the bore 62 through the passages 66 and 70, but will normally look these passages against fluid flow in the opposite direction. Similarly, the other valve assembly 88 will permit fluid flow to the ringshaped recess 64 through the passages 68 and 72, but will normally lock these passages against fluid flow in the opposite direction.

The intermediate unit section 44 has in its mounting surface 54 two spaced, machined annular recesses 100 and 102 which are in axial alignment with the respective check-valve assemblies 86 and 88, and are in this instance continued as diametrically-reduced bores or passages 104 and 106 to the opposite mounting surface 52. The annular recesses 100 and 102 constitute cylinder formations for plungers 108 and 110 which in this instance have shanks 112 and 114 and valve-opening pins 1 l6 and 118, respectively, of which the shanks 112 and 114 have in this instance a sliding fit in the bores 104 and 106. The intermediate unit section 44 is also provided with two through-passages or bores 120 and 122 which are spaced from the annular recesses 100 and 102 and are open at both mounting surfaces 52 and 54, and is further provided in its mounting surface 52 with grooves 124 and 126, of which groove 124 provides communication between through-passage 120 and check-valve assembly 86, while groove 126 provides communication between the other throughpassage 122 and the other check-valve assembly 88 (see also FIG. 3). Accordingly, on admission of fluid pressure into through-passage 120, check valve 86 will be opened for fluid flow to the bore 62 via the passages 66 and 70, while on admission of fluid pressure into the other through-passage 122, the other check valve 88 will be opened for fluid flow to the annular recess 64 via the passages 68 and 72.

The cover section 46 is provided in its mounting surface 50 with two through-holes 126' and 128' which are aligned and in communication with the throughpassages 120 and 122, respectively, in the intermediate unit section 44, and in this instance are threaded and connected with conduits 130 and 132. Further provided in the mounting surface 50 are two grooves 134 and 136, of which groove 134 provides communication between conduit and plunger 110, while groove 136 provides communication between the other conduit 132 and the other plunger 108 (see also FIG. 3).

The aforementioned orifices in the swivel coupling 16 that extend to the interior of the cylinder 12 lead from the adapter end 60 of the nonturning coupling part 20, of which one of these orifices in the coupling part 20 is a ring-shaped passage 140 formed in this instance between outer rings 142 and 144 and the outer peripheries of inner rings 146 and 148, of which the outer and'inner rings 144 and 148 are of any suitable wear-resistant material of good sealing properties, and are nested in the respective outer and inner rings 142 and 146. These sealing rings 144 and 148 bear against a slip ring 150 on the turning coupling part 18 for providing communication between the ring-shaped passage 140 in the non-turning coupling part 20 and an annular groove 152 in the operationally turning slip ring 150. The outer and inner rings 142 and 146 are fitted in the ring-shaped recess 64 in the unit section 42 in which there are also springs 154 and 156 that urge the rings 144 and 148 against the slip ring 150 with appropriate sealing pressure. The annular groove 152 in the slip ring 150 is in communication with the cylinder end 158 via a duct 160 in this slip ring and continuing duct 162 in the turning coupling part 18.

The other orifice part in the non-turning coupling part 20 is formed by a central duct 164 therein and a continuing duct 166 in a reduced shank 167 of the piston rod 28 which leads to the opposite cylinder end 168 via a transverse bore 170 in the rod 28 and a recess 172 in the piston 14, with the shank 167 having a sliding fit in an annular recess 174 in the turning coupling part 18.

For operation of the mechanism, the conduits 130 and 132 are connectible with a suitable fluid-pressure source, usually compressed air, by means of a two-way control valve (not shown). Thus, in on position of the control valve fluid pressure is admitted to the conduit 130 and the other conduit 132 is vented, and in the other valve position fluid pressure is admitted to the conduit 132 and the conduit 130 is vented. Assuming now that the cylinder end 168 is the chuck-closing end, and that the associated chuck is to be closed, the control valve is operated to admit fluid pressure from the source to the conduit 130 and vent the other conduit 132. The fluid pressure admitted to the conduit 130 passes through bore 120 and groove 124 to open check valve 86 and continue its pass to the cylinder end 168 via the passages 66, 70 and 62 in the unit 40 (FIG. 2), thence through the successive passages 178, 164, 166 and 170 (FIG. 1). The fluid pressure admitted to the conduit passes also through the groove 134 to the plunger 110 to open the other check valve 88 and thereby to vent the opposite cylinder end 158 through the straight passages 162 and 160, the ring-shaped passages 152 and 140, annular recess 64, passages 72 and 68, open check valve 88, groove 126, and passage 122 which is open to the vented conduit 132. Accordingly, on admission of fluid pressure to the conduit 130, fluid pressure passes to the cylinder end 168 and the other cylinder end 158 is simultaneously vented, with the result that the associated chuck is closed.

In order to open the associated chuck, the control valve is operated to admit fluid pressure from the source to the conduit 132 and vent the other conduit 130. As a result, fluid pressure passes to the cylinder end 158 via passage 122 and groove 126 to open check valve 88, thence through passages 68 and 70, recess 64, ring-shaped passages 140 and 152, and straight passages 160 and 162. Fluid pressure admitted to the conduit 132 also passes through groove 136 to the plunger 108 (FIGS. 2 and 3) for opening the check valve 86, and thereby vent the other cylinder end 168 via the passages 166, 164, 178, and 62 (FIG. 1), passages 70 and 66, the open check valve 86, groove 124 and passage 120 which is open to the vented conduit 130.

If after once closing the associated chuck on work with a safe grip, there should occur from any cause whatever a sudden pressure drop, or failure altogether, of the fluid source, or a leak anywhere in the fluid pressure line from the source to the check valve 86 which would cause the pressure of the fluid at this check valve to drop below the pressure of the operating fluid in the chuck-closing cylinder end 168, the check valve 86 will immediately-be spring-closed and thus lock the operating fluid in this cylinder end and hold it at its safe workgripping pressure, so that the work, when once safely gripped, may be turned at normal speed and machined while remaining safely gripped. It is, of course, advantageous to provide for ready indication to an operator of such pressure drop'or failure of the fluid source, or leak in the fluid line from the source to the check valve 86, in order to avoid renewed closing of the chuck with less-than-safe pressure of the fluid, and this may be achieved by connecting with this fluid line, preferably close to the check valve 86, any suitable pressuresensing instrumentality (not shown) to visibly indicate the sensed pressure or to activate any suitable alarm device when the sensed pressure is below safe workgripping pressure.

If the opposite cylinder end 158 should be the chuckclosing end, then the other check valve 88 will similarly respond to a pressure drop or failure of the fluid, or a leak in the fluid line from the source to this check valve, by closing and thereby locking the operating fluid in the chuck-closing cylinder end 158 and holding it at its safe work-gripping pressure.

While the described fluid-lock unit 40 is adapted to the non-turning part of the swivel coupling, FIG. 7 shows a modified fluid-lock unit 40a which in all respects is like the unit 40, except that its end section 420 also embodies the non-turning coupling part 20a for assembly of the unit 40 with the rest of the mechanism by connection of its coupling part 20a with the turning coupling part 18a of the mechanism.

The described fluid-lock unit, by being operationally stationary, is further advantageous in that the same may perform a further function of safe chuck operation, namely to sense the actual pressure of the operating fluid in the chuck-closing cylinder end, and to visibly indicate the sensed pressure at all times and/or sound an alarm or stop the chuck drive when the sensed pressure is for any reason below safe. workthe chuck-closing cylinder end. This holds true even if there should develop a fluid leak in the swivel coupling with an ensuing pressure drop in the chuck-closing cylinder end, for substantially the same pressure drop would then also occur at the nearby pressure gauge 180, and it holds further true if a pressure drop in the operating fluid in the chuck-closing cylinder end is occasioned by fluid leakage across the piston to the other cylinder end on breakdown of the usual sealing ring in the piston, for example. Of course, the pressure gauge 180, by visibly indicating the pressure of the operating fluid in the chuck-closing cylinder end at any time, also affords detection of either or both of the fluid leaks just mentioned and thus makes for further enhanced safety in chuck operation.

This enhanced safety in chuck operation is carried further by associating with the pressure gauge 180 an electric alarm 186, such as a bell, for instance, having a circuit which comprises a lead 188 from one side of a power line 198, a contact 192 at the dial 182, a pointer 184, a lead 194 from the pointer 184 to the alarm 186, and a lead 196 from the alarm 186 to the other side of the power line. The contact 192 may be set at a pressure indication on the dial which denotes a given lower-than-permissible, but not yet dangerously low, alarm pressure, whereby on a pressure drop of the fluid sensed by the pressure gauge to this given alarm pressure, the alarm 196 will sound. To avoid sounding of the alarm 186 on releasing gripped work gripping pressure. Thus, FIG. 4 shows fluid-operating mechanism having a fluid-lock unit 4812 which may in all respects be like the described unit 40, for example, except that the plug has been removed from the bore 70b and there is connected therewith a pressure gauge 186 with a graduated dial 182 and a pointer 184. The bore 701; forms in this instance a part ofthe fluid passage to the chuck-closing cylinder end of the mechanism, so that the pressure gauge 180 visibly indicates at any time the actual pressure of the operating fluid in and while the chuck-closing cylinder end is vented, there is preferably interposed in the lead a switch 198 which by suitable provisions (not shown) is open except while work is gripped by the associated chuck.

Safe chuck operation is carried still further with the fluid-lock unit 40c of FIG. 5, in which the bore c is connected with a pressure-sensing instrumentality 200 in the exemplary form of a cylinder 202 with a piston 204 therein, with one cylinder end 206 being in communication with the bore 700 and thus subjected to fluid pressure therein. The piston 204 is by a calibrated spring 208 urged toward the cylinder end 206, and carries the movable contract 210 of a switch 212. As long as fluid pressure in the bore 70d and, hence, in the chuck-closing cylinder end, is at a given safe workgripping pressure, this fluid pressure will cause the piston 284 to keep the switch 212 closed, as shown, with this switch 212 being in series connection with a main switch 214 for the power drive of the chuck. If for any reason the pressure of fluid in the bore 700 and, hence, in the chuck-closing cylinder end, should drop below the given safe work-gripping pressure during chuck operation, the spring 208 will urge the piston 204 from its shown switch-closing position, whereby immediately on opening of the switch 212 the power drive of the chuck will be stopped even though the main switch 214 remains closed.

' The fluid-lock unit, by being operationally stationary, also lends itself to a featured high-low chuck operation. Such chuck operation is highly desirable for many applications requiring an initial heavy grip on work followed by a lighter work grip without stopping the chuck drive. Just one example of such an application is specified external rough-machining of internally gripped sleeve-type work to a smaller outer diameter requiring a heavy work grip, followed by specified external finish-machining of the internally-gripped work requiring a lighter work grip to avoid fracturing of the progressively more fragile work. Such chuck operation requires, for initial rough machining of work, operating fluid of a given high pressure in the chuck-closing cylinder end of fluid-operating mechanism, and requires, for the following finish-machining of the work, fluid of a given lower operating pressure in this chuck-closing cylinder end. The change from the high pressure to the lower pressure of the operating fluid in the chuckclosing cylinder end is achieved by bleeding fluid from this cylinder end while leaving the other cylinder end vented. However, while the given lower pressure is fully adequate to hold the work safely gripped for finishmachining, mere reduction of the pressure of the fluid in the chuck-closing cylinder end to the given lower pressure by bleeding this cylinder end, is mostly insufficient to permit operating chuck parts to break loose from their tight binding engagement ensuing from the heavy work grip exertion. Accordingly, in order to permit these operating chuck parts to break loose from their tight binding engagement and thereby relax the heavy work grip in the first place, the pressure of the fluid in the chuck-closing cylinder end must be reduced from the given high pressure momentarily to a given minimum pressure below the given lowerpressure, with the chuck responding to this minimum pressure in re laxing the heavy work grip. Accordingly, for high-low chuck operation, the fluid-operating mechanism. must function to first admit to the chuck-closing cylinder end fluid under the given high pressure, then bleed fluid from this cylinder end until the pressure of the fluid therein drops to the given minimum pressure, and then immediately admit to this cylinder end fluid at the given lower operating pressure.

FIG. 6 shows diagrammatically fluid-operating mechanism, including a fluid-lock unit 40d, for high-low chuck operation as just explained. The fluid-lock unit 40d may in all respects be like the unit 40 of FIGS. 1 to 3 or the unit 40a of FIG. 7, and all there is shown of this unit is the bore 70d which in this instance is part of the fluid passage to the chuck-closing cylinder end, and the conduits 130d and 132d which are parts of the fluid passages to the chuck-closing and chuck-opening cylinder ends, respectively. These conduits 130d and 132d are shown connected to ports 220 and 222 in the body 224 of a two-way valve 226, with this body having another port 228 and a vent opening 230, and the tumable valve member 232 has two orifices for connecting certain of the ports with each other and with the vent opening 230. Associated in this instance with the valve 226 is another two-way valve 240 the body of which has three ports 242, 244 and 246 and a vent opening 248, and the tumable valve member thereof has two orifices for connecting certain of the ports with each other and with the vent opening 248. In this instance, the ports 228 and 242 of the valves 226 and 240 are connected with each other through a conduit 250, and the port 246 of valve 240 is through a conduit 252 connectedwith any suitable fluid-pressure source at the given high pressure.

High-low chuck operation also requires another fluid-pressure source at the given lower pressure. To this end, there is provided a pressure-reducing valve 254 with an inlet and an outlet, of which the inlet is through a conduit 256 connected with the port 244 in the valve'240. Accordingly, on shifting valve 240 into the position other than that shown, fluid from the highpressure source is through conduits 252 and 256 admitted to the inlet of the pressure-reducing valve 254, so that the fluid pressure in the outlet of this valve is at the given lower pressure and, hence, constitutes the fluidpressure source of the given lower pressure.

High-low chuck operation further requires certain valve and other instrumentalities. These are a first" valve 258, a second valve 260, a third" valve 262, and an instrumentality 264.

The first valve 258 has in its body two ports 266 and 268 and a vent opening 270, and the shiftable valve member 272 is normally spring-urged into the full-line position in which to intercept communication between port 268 and vent opening 270, and is on admission of fluid pressure into the other port 266 shifted to its other, dot-and-dash line position in which to provide communication between port 268 and vent opening 270. Port 170 is in open communication with bore d and, hence, with the chuck-closing cylinder end.

The second valve 260 has in its body three ports 274, 276 and 278 and a vent opening 280, and the shiftable valve member 282 is normally spring-urged into the full-line position in which to provide communication between the ports 274 and 278, and is shiftable into the other, dot-and-dash line position in which to provide communication between the ports 274, 276 and provide also communication between port 278 and vent opening 280. Port 278 is through a conduit or first duct 284 connected with the port 266 in the first valve 258, while port 274 is connected with the outlet of the pressure-reducing valve 254 by a conduit or third duct" 286.

The third valve 262 has in its body four ports 288, 290, 292 and 294 and a vent opening 296, and the shiftable valve member 298 is normally spring-urged into the full-line position in which to provide communication between the ports 290 and 292, and is on admission of fluid pressure to the port 294 shifted to its other, dot-and-dash line position in which to provide communication between the ports 288 and 290 and also provide communication between port 292 and vent opening 296. Port 290 is through a conduit or fourth duct 300 connected with the bore 70d and, hence, with the chuck-closing cylinder end, while the ports 288 and 294 are connected with branches 302 and 304, respectively, of a conduit 306 which, in turn, is connected with the port 276 in the second valve 260.

The instrumentality 264 provides a cylinder 308 and a piston 310 therein which is normally urged by a spring 312 against the cylinder end 314. The cylinder 308 has in its end 314 a port 316 which through a conduit 318 is connected with the port 292 in the third valve 262. The piston 310 carries the movable contact 320 of a switch 322 which is open, as shown, when the piston 310 is shifted to the position shown by fluid pressure inthe cylinder end 314. The switch 322 is in the circuit of a relay 324 which includes an armature 326 carried by the shiftable valve member 282 of the second valve 260. Assuming that the pressure-reducing valve 254 is of a type passing fluid in the direction of the arrows, but not in the opposite direction, there is provided a check valve 328 in bypass relation with the pressure-reducing valve 254 to permit venting of the third duct 286 via the check valve 328.

Following is a description of a high-low chuckoperating performance of the mechanism. In order to chuck work with the heavy grip and retain the heavy work grip during initial rough-machining of the work,

the two-way control valves 240 and 226 are set, as shown, toadmit fluid pressure from the high-pressure source to the chuck-closing cylinder end of the mecha nism, via conduit 252, valve 240, conduit 250, valve 226, and conduit 130d which through the fluid-lock unit 40d, including bore 70d, communicates with the chuck-closing cylinder end, while the opposite, chuckopening cylinder end is then vented via the fluid-lock unit 40d, conduit 132d and vent opening 230 in control valve 226. While the work is thus being gripped and held gripped with the heavy grip, the first, second and third valves 258, 260 and 262 and the instrumentality 264 assume the respective full-line positions in which the first valve 258 prevents venting of the chuckclosing cylinder end, and the third valve 262 subjects the piston 310 of the instrumentality 264 to fluid under the pressure of the fluid in the chuck-closing cylinder end to hold switch 322 open.

With rough-machining of the work finished, the heavy work grip is relaxed and then held at the lighter work grip required for finish-machining the work. To this end, control valve 240 is shifted to its other position in which to provide communication between the high-pressure fluid source and pressure-reducing valve 254 via conduit 252, the ports 246 and 244 of valve 240, and conduit 256, thereby passing from the outlet of this pressure-reducing valve fluid at the given lower pressure. In thus shifting control valve 240 to its other position, and leaving the other control valve 226 in the position shown, the conduit 130d of the fluid-lock unit 40d is vented via valve 226, conduit 250 and port 242 and vent opening 248 of control valve 240. However, even though the conduit 1304 of the fluid-lock unit 40d is then vented, the high-pressure operating fluid in the chuck-closing cylinder end remains locked therein by the check valve in the fluid-lock unit which is associated with this chuck-closing cylinder end.

Fluid passing from the outlet of the pressurereducing valve 254 at the given lower pressure passes to the first valve 258 via the third duct 286, the second valve 260, and the first duct 284, thereby opening this first valve for bleeding operating fluid from the chuckclosing cylinder end via bore 70d and port 268 and vent opening 270 of the first valve. With the cylinder end 314 of the instrumentality 264 being then also connected with the bore 70d via conduit 318, the third valve 262 and the fourth duct 300, there takes place an equal pressure drop of the fluid in the cylinder end 314 and in the chuck-closing cylinder end on thus bleeding fluid from the latter. This fluid-pressure drop continuous until the spring 312 forces the piston 310 of the instrumentality 264 toward the cylinder end 314 to an extent where the associated switch 322 is closed, with the spring 312 being calibrated to close this switch 322 at the given minimum pressure of the fluid in the cylinder end 314, andthis given minimum pressure, being less than the given lower pressure, is adequate to permit the operating chuck parts to break loose from their tight binding engagement and relax the heavy work grip sufficiently to avoid in any event fracture of the now more fragile work prior to and during finish-machining of the same. It is to be distinctly understood, however, that the pressure drop of the fluid involved is reached only momentarily, for bleeding of fluid from the chuckclosing cylinder end is stopped and fluid under the given lower pressure is admitted to the latter the moment switch 322 is closed.

Closure of the switch 322 in this manner closes the circuit of the solenoid 324 which causes a shift of the second valve 260 to its dot-and-dash line position, in which port 266 of the first valve 258 is vented through the vent opening 280 in the second valve 260 to permit spring-closure of this first valve, and fluid under the given lower pressure in the third duct 286 is through this second valve, conduit 306 and branch 304 thereof admitted to the port 294 in the third valve 262 to shift the latter to its dot-and-dash line position. With this third valve 262 in its dot-and-dash line position, fluid under the given lower pressure in the conduit 306 is, through its other branch 302, valve 262, fourth conduit 300 and bore 70d also admitted to the chuck-closing cylinder end for applying to the work the lighter grip which safely holds the work for finish-machining without any danger of fracturing the work. Further, simultaneously with the shift of the third valve 262 into its dotand-dash line position, this valve interrupts communication between the fourth conduit 300 and the conduit 318 which leads to the cylinder end 314 of the instrumentality 264, and provides communication between this conduit 318 and the vent opening 296 in the third valve 262, thus venting the cylinder end 314 and spring-holding piston 310 in position to keep switch 322 closed. With the switch 322 being thus held closed, the second valve 260 remains in its dot-and-dash line position in which the chuck-closing cylinder end remains subjected to fluid under the given'lower pressure, thereby keeping the safe lighter grip on the work for its finish machining.

Once the work is finish-machined and the .chuck drive stopped, the work is released from the chuck. This is achieved preferably by first returning control valve 240 to its position as shown, and immediately thereafter shifting the other control valve 226 to the position other than that shown, thereby providing communication between the high-pressure fluid source and conduit 132d of the fluid-lock unit via conduit 252, ports 246 and 242 of valve 240, conduit 250, and ports 228 and 222 of valve 226, and simultaneously venting the other conduit d of the fluid-lock unit 40d via port 220 and vent opening 230 in valve 226. Further, in thus shifting the control valve 240, the same on the one hand intercepts communication between the highpressure fluid supply and conduit 256 so that fluid under the given lower pressure no longer passes to the chuck-closing cylinder end, and on the other hand provides communication between conduit 256 and vent opening 248 in the valve to vent port 294 of the third valve 262 via conduit branch 304, conduit 306, the second valve 260, the third duct 286, check valve 328, conduit 256 and control valve 240, and thereby permit spring-return of the third valve 262 to its full-line position. I

In providing communication between the highpressure fluid source and conduit 132d of the fluid-lock unit 40d and simultaneously venting the other conduit 130d of this fluid-lock unit in the manner just described, operating fluid under high pressure is admitted to the chuck-opening cylinder end and the opposite, chuck-closing cylinder end is simultaneously vented as will be readily understood from the preceding description of the operation of the fluid-lock unit, resulting in release of the work from the chuck. In view of the above-mentioned preferred sequential shift of the control valves 240 and 226, spring-retum in the manner just described of the third valve 262 to its full-line position will occur just before the chuck-closing cylinder end is vented, so that the cylinder end 314 of the instrumentality will again be subjected to fluid under the given lower pressure to cause opening of the circuit of the solenoid 324 at the switch 322 and, hence, springretum of the second valve 260 to its full-line position, but this fluid will then temporarily remain in this cylinder end until the latter is vented simultaneously with the chuck-closing cylinder end via the fluid-lock unit 40d, at which time the solenoid circuit will be reclosed and the second valve 260 shifted to its dot-and-dash line position. However, reclosure of the solenoid circuit and ensuing shift of the second valve 260 in no wise interferes with proper high-low chuck operation, for even though this second valve 260 remains in its dotted-line position during the interim between work-release from the chuck and gripping new work in the chuck, the first and third valves 258 and 262 and the instrumentality 264 are during this interim in positions to start a new high-low chuck operation, meaning that while the instrumentality 264 will during this interim keep the solenoid circuit closed, this instrumentality will on the start of the next high-low chuck operation respond immediately to renewed admission of high-pressure to the chuck-closing cylinder end in opening the solenoid circuit and permit spring-return of the second valve 260 to its full-line position. Hence, to start a new high-low chuck operation, it is merely necessary to return control valve 224 to the position shown, and leave the other control valve 240 in the position shown, whereupon high-low chuck operation identical with the one described will take place.

The first, second and third valves 258, 260, 262, the instrumentality 264, the pressure-reducing valve 254, and their conduit connections, termed collectively a high-low chuck-operating device" for simplicity of expression, may be provided outside the fluid-lock unit 40b, or may be embodied with the fluid-lock unit 40b in one self-contained unit 330.

What is claimed is:

l. Fluid-operating mechanism for a chuck, comprising an operationally turning cylinder with opposite first and second ends and a piston therein; a swivel coupling having companion parts, of which one coupling part is operationally stationary, and the other coupling part is turnable with said cylinder and has first and second orifices leading to said first and second cylinder ends, respectively, said one coupling part having first and second apertures in communication with said first and second orifices, respectively, first and second conduit connections, first and second fluid passages leading from said first and second conduit connections to said first and second apertures, respectively, a check valve interposed in said first passage and normally closed against fluid flow in said first passage from said first cylinder end, a movable plunger operatively aligned with said check valve and having an end adapted on subjection to fluid pressure to move said plunger for opening said check valve, a port branching from said second passage and leading to said plunger end; first valve means shift able into first, second and third positions, with said valve means in said first position providing communication between a first fluid source of a given high-level pressure and said first conduit connection and simultaneously venting said second conduit connection, and in said second position providing communication between said first fluid source and said second conduit connection and simultaneously venting said first conduit connection; and a device for decreasing the pressure of operating fluid in said first cylinder end from said high-level pressure to a certain low-level pressure, including said first valve means, and further providing a vent, second valve means normally closed to intercept communication between said vent and first aperture, and having an end adapted on subjection to fluid pressure to open said second valve means for providing communication between said vent and first aperture, third, fourth and fifth passages, of which said fifth passage leads to said end of said second valve means, and said fourth passage leads to said first aperture, third valve means normally urged into a first position in which to provide communication between said third and fifth passages, and shiftable into a second position in which to provide communication between said third and fourth passages and vent said fifth passage, with said first valve means in said third position providing communication between a second fluid source of said certain low-level pressure and said third passage, intercepting communication between said first fluid source and said first conduit connection, and venting said second conduit connection, and control means operative in said third position of said first valve means to shift said third valve means into said second position on a pressure drop of fluid in said first aperture to a given minimum level below said low-level pressure, and retain it in said second position while said first valve means is in said third position.

2. Fluid-operating mechanism as in claim 1 in which said control means provides an instrumentality including a cylinder chamber with another piston therein, and a spring urging said other piston to one end of said chamber, and operative on movement of said other piston to said one chamber end to shift said third valve means into said second position, and fourth valve means interposed in said fourth passage and dividing the latter into first and second branches of which said second branch extends between said fourth valve means and first aperture, with said fourth valve means being normally urged into a first position in which to intercept communication between said branches and provide communication between said second branch and said one chamber end, and being by fluid pressure in said first branch shifted into a second position in which to provide communication between said branches and vent said one chamber end, with said spring being calibrated to force said other piston to said one chamber end when the pressure of fluid in the latter is at and below said minimum level.

3. Fluid-operating mechanism as in claim 2, which further provides a pressure-reducing valve with a fluid inlet and outlet, of which said outlet communicates with said third passage, and said first valve means in said third position providing communication between said first fluid source and said fluid inlet, intercepting communication between said first fluid source and said first conduit connection, and venting said second conduit connection, so that on connection of said inlet with said first fluid source fluid in said outlet constitutes said second fluid source of said low-level pressure.

* k I III 

1. Fluid-operating mechanism for a chuck, comprising an operationally turning cylinder with opposite first and second ends and a piston therein; a swivel coupling having companion parts, of which one coupling part is operationally stationary, and the other coupling part is turnable with said cylinder and has first and second orifices leading to said first and second Cylinder ends, respectively, said one coupling part having first and second apertures in communication with said first and second orifices, respectively, first and second conduit connections, first and second fluid passages leading from said first and second conduit connections to said first and second apertures, respectively, a check valve interposed in said first passage and normally closed against fluid flow in said first passage from said first cylinder end, a movable plunger operatively aligned with said check valve and having an end adapted on subjection to fluid pressure to move said plunger for opening said check valve, a port branching from said second passage and leading to said plunger end; first valve means shiftable into first, second and third positions, with said valve means in said first position providing communication between a first fluid source of a given high-level pressure and said first conduit connection and simultaneously venting said second conduit connection, and in said second position providing communication between said first fluid source and said second conduit connection and simultaneously venting said first conduit connection; and a device for decreasing the pressure of operating fluid in said first cylinder end from said high-level pressure to a certain low-level pressure, including said first valve means, and further providing a vent, second valve means normally closed to intercept communication between said vent and first aperture, and having an end adapted on subjection to fluid pressure to open said second valve means for providing communication between said vent and first aperture, third, fourth and fifth passages, of which said fifth passage leads to said end of said second valve means, and said fourth passage leads to said first aperture, third valve means normally urged into a first position in which to provide communication between said third and fifth passages, and shiftable into a second position in which to provide communication between said third and fourth passages and vent said fifth passage, with said first valve means in said third position providing communication between a second fluid source of said certain low-level pressure and said third passage, intercepting communication between said first fluid source and said first conduit connection, and venting said second conduit connection, and control means operative in said third position of said first valve means to shift said third valve means into said second position on a pressure drop of fluid in said first aperture to a given minimum level below said low-level pressure, and retain it in said second position while said first valve means is in said third position.
 2. Fluid-operating mechanism as in claim 1 in which said control means provides an instrumentality including a cylinder chamber with another piston therein, and a spring urging said other piston to one end of said chamber, and operative on movement of said other piston to said one chamber end to shift said third valve means into said second position, and fourth valve means interposed in said fourth passage and dividing the latter into first and second branches of which said second branch extends between said fourth valve means and first aperture, with said fourth valve means being normally urged into a first position in which to intercept communication between said branches and provide communication between said second branch and said one chamber end, and being by fluid pressure in said first branch shifted into a second position in which to provide communication between said branches and vent said one chamber end, with said spring being calibrated to force said other piston to said one chamber end when the pressure of fluid in the latter is at and below said minimum level.
 3. Fluid-operating mechanism as in claim 2, which further provides a pressure-reducing valve with a fluid inlet and outlet, of which said outlet communicates with said third passage, and said first valve means in said third positiOn providing communication between said first fluid source and said fluid inlet, intercepting communication between said first fluid source and said first conduit connection, and venting said second conduit connection, so that on connection of said inlet with said first fluid source fluid in said outlet constitutes said second fluid source of said low-level pressure. 